Automapper 一源多目的地和派生类

Question

我正在尝试将一个实体对象映射到不同的视图模型。我有一个基础视图模型和其他两个从基础派生的视图模型。视图模型是通过工厂方法在运行时基于它们的类型属性创建的。派生视图模型没有单独的实体，源实体具有派生视图模型的所有属性。问题是 Automapper 能够通过工厂方法创建正确的对象，但派生对象中的属性根本没有映射。仅映射基本视图模型的属性。

示例实体：

public class VehicleEntity
{
    public int Type { get; set; }
    public int LoadCapacity { get; set; }
    public TrailerEntity Trailer { get; set; }
}

public class TrailerEntity
{
    public int Capacity { get; set; }
}

查看模型：

public class VehicleVM
{
    public int Type { get; set; }
}

public class CarVM: VehicleVM
{
    public TrailerVM Trailer { get; set; }
}

public class TruckVM : VehicleVM
{
    public int LoadCapacity { get; set; }
}

public class TrailerVM
{
    public int Capacity { get; set; }
}

public static class VehicleFactory
{
    public static VehicleVM GetInstance(int type)
    {
        switch (type)
        {
            case 1:
                return new CarVM();
            case 2:
                return new TruckVM();
            default:
                return new VehicleVM();
        }
    }
}

最后是映射：

        List<VehicleEntity> vehicleList = new List<VehicleEntity>();
        vehicleList.Add(new VehicleEntity()
        {
            Type = 1,
            LoadCapacity = 0,
            Trailer = new TrailerEntity()
            {
                Capacity = 120
            }
        });

        vehicleList.Add(new VehicleEntity()
        {
            Type = 2,
            LoadCapacity = 8000,
            Trailer = null
        });

        var config = new MapperConfiguration(cfg =>
        {
            cfg.CreateMap<VehicleEntity, VehicleVM>()
                .ConstructUsing((Func<VehicleEntity, VehicleVM>)(rc => VehicleFactory.GetInstance(rc.Type)))
                .Include<VehicleEntity, TruckVM>()
                .Include<VehicleEntity, CarVM>();
            cfg.CreateMap<VehicleEntity, TruckVM>();
            cfg.CreateMap<VehicleEntity, CarVM>();
            cfg.CreateMap<TrailerEntity, TrailerVM>();
        });

        IMapper mapper = config.CreateMapper();
        var vehicleVMs = mapper.Map<List<Data.VehicleEntity>, List<VehicleVM>>(vehicleList);

在上面的示例中，只有 Type 属性映射到 CarVM 和 TruckVM。其他属性不是...我也尝试使用 ForMember 方法来映射来自源实体的派生类属性，但没有运气。

cfg.CreateMap<VehicleEntity, TruckVM>().ForMember(dst => dst.LoadCapacity, opt => opt.MapFrom(src => src.LoadCapacity));

有可能实现吗？

Answer 1

您可以使用以下配置

var config = new MapperConfiguration(
    cfg =>
    {
        cfg.CreateMap<VehicleEntity, VehicleVM>()
            .ConstructUsing(rc => VehicleFactory.GetInstance(rc.Type))
            .BeforeMap((s, d, c) => c.Mapper.Map(s, d));

        cfg.CreateMap<VehicleEntity, TruckVM>();
        cfg.CreateMap<VehicleEntity, CarVM>();
        cfg.CreateMap<TrailerEntity, TrailerVM>();
    });

在这种情况下，ConstructUsing 根据 Type 属性创建适当的目标对象，然后在 BeforeMap 中将源 VehicleEntity 实例映射到创建的目标对象。您也可以在 AfterMap 方法中进行。

或者您可以立即在ConstructUsing中创建目标对象并在其上映射源

var config = new MapperConfiguration(
    cfg =>
    {
        cfg.CreateMap<VehicleEntity, VehicleVM>()
            .ConstructUsing((rc, context) => context.Mapper.Map(rc, VehicleFactory.GetInstance(rc.Type)));

        cfg.CreateMap<VehicleEntity, TruckVM>();
        cfg.CreateMap<VehicleEntity, CarVM>();
        cfg.CreateMap<TrailerEntity, TrailerVM>();
     });